Inspired by the replies I got, I attacked the problem again this morning. I was prepared to wire the lights temporarily as Bob suggested (to the wiper motor) in order to pass the upcoming inspection.

Solving the problem was a lot easier once I had a clearer picture of how the wiring is supposed to work. In my ignorance I initially thought the two wires (in one sheath) coming through the left side wire was connected in a loop. They are not, both are positive. One powers the demist on the left side of the window, which is grounded to the door on the right side. The other wire powers the license plate lights, which are also grounded to the door.

So one of the two wires through the left hinge did not work, easily established by measuring between wire and ground with lights turned on. I suspected a broken wire as suggested, but once I removed the car's inner ceiling the problem - and the solution - stared me in the face: One of the connectors was not connected! It was just a matter of joining the connectors and hey presto - license plate lights!

A big thanks for your kind assistance.
The car should pass with flying colors now.

Regards,
Erling.
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